5, and giving a feed by advancing the poppet screw; the
irill being first used, and the countersink afterward.
jntreing Machine.—This is a simple but useful con-
:e for rapidly preparing work for the lathe. The work is
in a concentric chuck A, Fig. 772, and a V support B ; the
being raised or lowered till the bar is level. The drill,
ig rapidly, is now advanced to the work by the lever, and
•untersink and plain hole both drilled at one time by means
: special drill-point shewn.
entre-grinding Wheel.—The common method of trueing
he centres is to soften them by heating, turn them up, and